Otitis Externa

Otitis Externa is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

Inflammation of the external auditory canal:

  • Acute diffuse otitis externa: the most common form; an infectious process; usually bacterial; occasionally fungal (10%)
  • Acute circumscribed otitis externa: synonymous with furuncle; associated with infection of the hair follicle, a superficial cellulitic form of otitis externa
  • Chronic otitis externa: same as acute diffuse but of longer duration (>6 weeks)
  • Eczematous otitis externa: may accompany typical atopic eczema or other primary skin conditions
  • Necrotizing malignant otitis externa: an infection that extends into the deeper tissues adjacent to the canal; may include osteomyelitis and cellulitis; rare in children
  • System(s) affected: skin/exocrine
  • Synonym(s): swimmer’s ear

Epidemiology

Incidence
  • Unknown; higher in the summer months and in warm, wet climates
  • Predominant age: all ages
  • Predominant sex: male = female

Prevalence
  • Acute, chronic, and eczematous: common
  • Necrotizing: uncommon

Etiology and Pathophysiology

  • Acute diffuse otitis externa
    • Traumatized external canal (e.g., from use of cotton swab)
    • Bacterial infection (90%): Pseudomonas (67%), Staphylococcus, Streptococcus, gram-negative rods
    • Fungal infection (10%): Aspergillus (90%), Candida, Phycomycetes, Rhizopus, Actinomyces, Penicillium
  • Chronic otitis externa: bacterial infection: Pseudomonas
  • Eczematous otitis externa (associated with primary skin disorder)
    • Eczema
    • Seborrhea
    • Psoriasis
    • Neurodermatitis
    • Contact dermatitis
    • Purulent otitis media
    • Sensitivity to topical medications
  • Necrotizing otitis externa
    • Invasive bacterial infection: Pseudomonas, increasing incidence of methicillin-resistant Staphylococcus aureus (MRSA)
    • Associated with immunosuppression

Risk Factors

  • Acute and chronic otitis externa
    • Traumatization of external canal
    • Swimming
    • Hot, humid weather
    • Hearing aid use
  • Eczematous: primary skin disorder
  • Necrotizing otitis externa in adults
    • Advanced age
    • Diabetes mellitus (DM)
    • Debilitating disease
    • AIDS
    • Immunosuppression
  • Necrotizing otitis externa in children (rare)
    • Leukopenia
    • Malnutrition
    • DM
    • Diabetes insipidus

General Prevention

  • Avoid prolonged exposure to moisture.
  • Use preventive antiseptics (acidifying solutions with 2% acetic acid [white vinegar] diluted 50/50 with water or isopropyl alcohol or 2% acetic acid with aluminum acetate [less irritating]) after swimming and bathing.
  • Treat predisposing skin conditions.
  • Eliminate self-inflicted trauma to canal with cotton swabs and other foreign objects.
  • Diagnose and treat underlying systemic conditions.
  • Use ear plugs when swimming.

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